Not able to access 'initparam' in Servlet

Question

I am learning servlets and I created a sample sevlet and created a initparam called 'message' using annotation. I am trying to access that param in doGet() method but getting nullPointerException. What can be the problem? The code is given below:

@WebServlet(
        description = "demo for in it method", 
        urlPatterns = { "/" }, 
        initParams = { 
                @WebInitParam(name = "Message", value = "this is in it param", description = "this is in it param description")
        })
public class DemoinitMethod extends HttpServlet {
    private static final long serialVersionUID = 1L;
    String msg = "";

    /**
     * @see HttpServlet#HttpServlet()
     */
    public DemoinitMethod() {
        super();
        // TODO Auto-generated constructor stub
    }

    /**
     * @see Servlet#init(ServletConfig)
     */
    public void init(ServletConfig config) throws ServletException {
        msg = "Message from in it method.";
    }

    /**
     * @see HttpServlet#doGet(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doGet(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        PrintWriter out = response.getWriter();
        out.println(msg);

        String msg2 = getInitParameter("Message");
        out.println("</br>"+msg2);
    }

    /**
     * @see HttpServlet#doPost(HttpServletRequest request, HttpServletResponse response)
     */
    protected void doPost(HttpServletRequest request, HttpServletResponse response) throws ServletException, IOException {
        // TODO Auto-generated method stub
        doGet(request, response);
    }

}

Answer 1

You have redefined the init method in your servlet so you need to call init method of GenericServlet class.

ex:

public void init(ServletConfig config) throws ServletException {
        super.init(config);

        msg = "Message from in it method.";
    }

To save you from having to do so, GenericServlet provide another init method without argument, thus you can override the one which doesn't take argument.

public void init(){
 msg = "Message from in it method.";
}

the init wihout arguement will be called by the one in GenericServlet.

Herer is the code of init method in GenericServlet:

public void init(ServletConfig config) throws ServletException {
this.config = config;
this.init();
}